Plane.cs

using UnityEngine;
using System.Collections;

public class Plane : MonoBehaviour {
    private Vector2 v = new Vector2(10, 10);
    /*
    private float radius = 50;

    public float GetCircumference()
    {
        return 2 * radius * Mathf.PI;
    }
    */

    public void Start()
    {
    }
    public void Update()
    {

        if(transform.parent.localEulerAngles.x > 60 ||
           transform.parent.localEulerAngles.x < -60)
        {
            v = new Vector2(v.x, -v.y);
        }

        transform.parent.Rotate(new Vector3(v.y, v.x, 0) * Time.deltaTime);

        RaycastHit hit;
        if(Physics.Raycast(transform.position, transform.parent.position - transform.position,  out hit)) 
        {
            Debug.DrawRay(transform.parent.position, hit.point, Color.green, 5);
        }

    }
}